Spinal cord stimulation (SCS) with electrical pulses is an accepted technique to treat certain patients having symptoms or conditions such as chronic pain, Parkinson's Disease, incontinence and epilepsy, among others. The treatment involves delivery of electrical pulses at selected locations along the spinal cord by electrode leads that are implanted within and extend along the epidural space of the spine. When such treatment is beneficial, the patient will experience a sensation (paresthesia) as the discomfort or other symptom is relieved. Such leads may be temporarily or permanently implanted. An important part of the procedure is the placement of the lead to locate the electrodes at its distal end at precisely the right location to affect the desired nerves. That involves adjustment in the position of the lead and monitoring feedback from the patient to determine the best position for the lead. When the best position is determined the lead is fixed in place. Lead placement also may be conducted under fluoroscopic visualization.
Leads may be placed surgically or in a less invasive, percutaneous, procedure. The percutaneous procedure involves insertion of a hollow needle into the epidural space so that the lead can be advanced through the lumen of the needle and then longitudinally along the dura of the spinal cord to the intended region of the spinal column. Typically, the position of the lead must be adjusted by advancing or retracting the lead through the needle and testing the effect of applying electrical pulses at various locations and with varying signals.
The leads typically are constructed to include a flexible elongate polymeric shaft with a plurality of electrodes mounted, at spaced locations, on the shaft. The electrodes are connected to wires that extend through the catheter to the proximal end of the catheter where they may be connected to a pulse generator. Some leads also may be placed with the aid of a stylet that is disposed within a lumen of the lead and can be manipulated by the physician
Among the difficulties with placement of epidural SCS leads is that the transitions along the outer surface of the lead from polymer to electrode to polymer, etc. may have some irregularities that sometimes results in the transition regions of the catheter becoming caught or snagged on an edge of the needle, possibly damaging the catheter. This is particularly troublesome as the physician is attempting to adjust the position of the lead by advancing or retracting the lead through the needle. Although the needle may be provided with an elongate bevel at its distal end to enable the lead to bend at a relatively large radius to reduce snagging, it would be desirable, however, to provide additional means by which the advancement or retraction of the lead through the needle is made smooth and with still further reduced risk of catching. It is among the objects of at least the invention to provide improvements to that end.